Antiferromagnetic domain walls under spin-orbit torque
Domain walls in antiferromagnets under a spin-polarized current present dynamical behavior that is not observed in ferromagnets, and it is tunable by the current polarization. Precessional dynamics is obtained for perpendicular spin polarization. In-plane polarization gives propagating walls. We obtain the velocity as a function of current by a perturbation method for low velocities, and the wall profile is found to lack a definite parity. For high velocities, a power-law decay develops in the trailing tail of the wall. The main features of the wall profile are manifest in a direct solution of an equation that is valid in a limiting case. Oscillatory motion of domain walls is obtained for a spin polarization that has both perpendicular and in-plane components, and an analytical description is given. We discuss the modifications of the dynamics when a Dzyaloshinskii-Moriya interaction is present. Finally, we give the magnetization of the dynamical walls and find that this can become large, providing a potential method for observations.